In order to join the two ends of a rubber belt together and in the process provide a strong joint therebetween, it is necessary to provide the proper heat and pressure simultaneously at the region of the joint which heat and pressure, when properly applied, act to vulcanize the rubber to thereby bond the belt ends together to form a joint. Often, in order to strengthen the joint, rubber cement is used as well as the addition of splice rubber so as to ensure that sufficient rubber is present at the region of the joint so as to provide a strong joint.
In the prior art, various methods have been utilized in order to provide heat as well as pressure at the area of the proposed joint. For example, screw jacks, hydraulic cylinders, air cylinders, etc. have been utilized in the prior art to provide the appropriate pressure for vulcanization. Further, in order to provide the proper temperature for vulcanization, electrical heating as well as steam heating have been used. Thus, in known systems, there has always been a problem with coordinating the source of pressurization with the source of heating so as to properly vulcanize the belt ends so as to form a proper joint. Some of the specific problems encountered through the use of the above described means for pressurizing and heating the region of the joint are as follows:
(a) It is desirable in pressurizing the location where the joint is to be produced to be able to uniformly pressurize the region at a pressure of between 60 and 125 psi. As noted above, one method for pressurizing the region of the splice comprises the use of screw clamps. In order to produce the required surface pressure at the area of the splice using screw clamping, it is necessary to tighten the bolt to a predetermined torque which requires expensive torque-measuring devices with the further expense incurred for paying the operator of such devices. In such an operation, a large number of screws may be necessary so as to properly pressurize the entire surface area, and accordingly, it is a time consuming operation to ensure that each bolt carries its correct load. During the time that the curing of the splice takes place, it is necessary to repeatedly check each bolt so as to ensure that no relaxation of the pressure has occurred. A further problem arises from the fact that the screws may only be placed along the outer edges of the belt, thus necessitating the use of transverse beams of great rigidity so as to evenly spread the pressure created by the torqueing-down of the screws across the surface of the splice. In order to provide sufficient rigidity in the beam so as to perform its required function, such a beam must be made quite heavy and accordingly such a beam is quite difficult to handle.
As noted hereinabove, a further means known in the prior art for clamping splices comprises the use of either hydraulic or air pressure clamping thereof. When such systems are properly used, even surface pressure applied to the belt surfaces at the region of the splice is possible, but in order to utilize this type of clamping procedure, a large variety of additional equipment is required such as pumps, compressors, hydraulic or air cylinders and the necessary hoses and other connections. In one form of air clamping, a pressurized rubber bag is used so as to evenly distribute clamping pressure over the entire surface of the splice area and so as to enable the absorption of any undulations in the surfaces thereof. The major drawback to the use of a rubber bag is that due to the fact that the region wherein the rubber bag is utilized is also heated to high temperatures, thus the lifespan of such a rubber bag is extremely limited. Further, replacing such a rubber bag is extremely expensive.
(b) As stated hereinabove, in order to vulcanize the area of the splice within a reasonable time, temperatures on the order of 300.degree. to 360.degree. Farenheit must be applied to the splice. The most commonly utilized source of heat in the splicing of rubber belts comprises radiation heating with electrical power. The main drawback to the use of electricity as a source of heat is that the site where the splicing is to take place must be within close proximity of a suitable power supply for the electricity or otherwise a large, expensive mobile electrical generator must be provided. In most instances, the use of extremely long extension cables are necessary which results in large losses in voltage which thereby lowers the temperatures which may be provided through an electrical source. Thus, the time period for vulcanization may be several times that which would be preferred.
As stated hereinabove, a further source of heat utilized in the vulcanization of rubber comprises the use of steam. The main limitation to the use of steam appears to be the requirement for a separate boiler arrangement so as to provide the steam.
(c) The zone where the splicing is taking place must be cooled in a manner so as to enable the vulcanization process to be concluded without causing blisters on the splice area. In the prior art, various methods have been employed for introducing cooling air or water into the zone wherein the splicing is taking place so as to cool the splice area. Such methods have commonly required complicated hose connections, and further equipment which has rendered the entire process extremely cumbersome and difficult to easily complete.
Applicant is aware of U.S. Pat. No. 4,334,850 to Garabedian which is related to prior U.S. Pat. Nos. 3,383,265, 4,104,101 and 4,243,368. U.S. Pat. No. 4,334,850 discloses an apparatus for making a stress-free plastic article which includes an embodiment shown in particular in FIG. 4 specifically designed for uniting together a series of layers of plastic with a micro-porous parting sheet and a wire screen. The device includes flexible sacks which are made in the same manner as the flexible envelope described with regard to the embodiment of FIG. 1. The envelope shown in FIG. 1 is disclosed as being produced in one form thereof of copper or stainless steel in thicknesses of 0.020 inches to 0.060 inches. The sacks shown in FIG. 4 are mounted on support members for relative movement toward and away from one another and heating cores are embedded in the support portions to supply heat to the fluid located within the sacks to thereby heat the materials which are being connected together between the sacks. Alternatively, this patent discloses the use of steam or hot liquids as the pressurizing fluid in order to heat the sack disclosed in the FIG. 1 embodiment thereof. While there are similarities between the teachings of U.S. Pat. No. 4,334,850 and the present invention, several differences also exist which are believed to render the present invention patentably distinct therefrom. A first difference lies in the fact that U.S. Pat. No. 4,334,850 is drawn to an apparatus which causes the consolidation of plastic particles into an article of manufacture. This is quite different from the purposes of applicant who vulcanizes belt splices together. The process of vulcanizing is a process which involves non-reversible molecular linking. This is quite different from the concept of merely melting particles together. A further difference involves the fact that U.S. Pat. No. 4,334,850 only contemplates pressures of 50 psi or less. Further, even though U.S. Pat. No. 4,334,850 discloses the use of steam to provide both heat and pressure to one embodiment thereof, no correlation is made in the patent between the concepts of the specific ranges of pressure and temperature which are necessary so as to vulcanize a splice of a rubber belt or other rubber article.
In developing the present invention, applicant listed several desirable criteria which he decided should be fulfilled in a self-contained belt vulcanizing device which criteria are included in the present invention. These criteria are:
(1) simplicity in design and assembly; PA1 (2) the use of one source for both heat and pressurization of a splice; PA1 (3) simplicity of operation; and PA1 (4) cooling of the splice area should be accomplished without the use of any additional equipment. PA1 (1) A pair of opposed steam sacks are provided, each of which is made of an extremely thin metal skin which metal may preferably be stainless steel. The thickness of the metal skin is on the order of 0.030 inches. PA1 (2) Each steam sack is mounted on a frame device with the frame devices being reciprocable with respect to one another so as to enable adjustment of the spacing between the facing surfaces of the respective steam sacks. Thus, after the two ends of belt which are to be spliced together are placed between the steam sacks, the respective frames may be reciprocated so as to enable the engagement on opposite sides thereof by the opposed steam sacks. PA1 (3) A boiler is provided in conjunction with the present invention which enables water to be boiled to create sufficient steam so as to pressurize the steam sacks to the desired pressure while heating them to the desired temperature simultaneously. PA1 (4) A shut-off valve is provided in the system so that at the completion of the necessary vulcanizing time the pressurized steam may be retained within the steam sacks. The gradual cooling and condensation of the steam causes concurrent reduction in the pressure and temperature at the area of the splice to thereby allow the splice to come to a normal temperature and pressure while avoiding blistering at the region of the splice. PA1 (5) The system includes means for adjusting the pressure of the steam within the steam sacks to thereby accordingly vary the temperature to which the belt splice is exposed which thereby controls the time of vulcanization. Accordingly, the system may be adjusted to accommodate to differing widths and thicknesses of belts as well as being adjustable to provide differing vulcanization times for belts of similar characteristics.